2. If the weather gets colder, we'll turn on the heating.
Should -> the weather get colder, we'll turn on the heating.
3.If you had been there, you would have enjoyed it.
Had -> you been there, you would have enjoyed it.
4.If he had left earlier, he would have been on time.
Had -> he left earlier, he would have been on time.
5.If you fail to apologize, he will never forgive you.
Should -> you fail to apologise, he will never forgive you.
